Canada to ban 737 Max 8 and Max 9 aircraft from flying in Canadian airspace

The Canadian government said Wednesday it is temporarily grounding Boeing 737 Max 8 and Max 9 planes and barring them from the country's airspace, joining dozens of nations suspending service after the second fatal crash of the planes in less than five months.

"The advice the experts have provided is based on the information they have been receiving; the requirements for new procedures and training for Boeing 737 MAX 8 and 9 flight crews they have already put in place; and the latest information available from the incidents," Canadian Transport Minister Marc Garneau said in a statement.

Canada's decision made the United States a notable holdout for allowing the Boeing planes to fly as investigators seek clues as to what brought down an Ethiopian Airlines 737 Max 8 shortly after takeoff on Sunday, killing all 157 people on board. The Federal Aviation Administration on Tuesday reiterated its stance on the plane, saying it saw no reason to order the jets be taken out of service.

Canada's transportation ministry said it's immediately restricting all Boeing 737 MAX 8 and 9 aircraft "from arriving, departing, or overflying Canadian airspace."

Dozens of countries and airlines spanning from China to Mexico and Europe have grounded the planes this week.

The crash of Ethiopian Airlines Flight 302 came less than five months after a Lion Air Boeing 737 Max 8 plunged into the Java Sea minutes into the flight, killing all 189 people on board.

Both planes were new, delivered from Boeing just months before their doomed flights.

Air Canada has 24 Boeing 737 Max 8 planes in its fleet and said it would waive cancellation and ticket-change fees for customers affected by the government order. It warned travelers that its Boeing 737 Max planes carry on average 9,000 to 12,000 passengers daily so "customers can expect delays in rebooking and in reaching Air Canada call centres and we appreciate our customers' patience.

Boeing investors lost $26.6 billion in the first two trading days this week with shares sliding 11 percent from $422.54 Friday to $375.41 at Tuesday's close. The drop cut the company's market value from $238.7 billion to $212.1 billion over Monday and Tuesday. Its stock was up 0.1 percent in Wednesday afternoon trading.

-CNBC's Jessica Bursztynsky contributed to this report.